This invention relates generally to storage tanks and more particularly concerns collapsible portable tanks for storing liquids.
Collapsible portable tanks for storing liquids are well known and have changed very little over the years. They are, for example, often used by firefighters as a water reservoir at the scene of a fire. It is desirable that they can be quickly opened, emptied and collapsed by one or two workers, that they be lightweight but durable and that they be inexpensive.
Modern tanks have liners which include side walls and a floor panel which are made from a single sheet of material. The side walls are supported by a frame while the floor panel rests on the ground. Since the floor panel incurs the most significant abuse, the entire liner is made of material of sufficient weight to meet the requirements for the floor panel. This needlessly increases the total cost of the entire liner. Furthermore, since the sheet of material is folded to form the side walls and floor panel of the liner, excess pleats of material are created in each corner of the tank. The excess material adds unnecessarily to the weight of the liner and to the bulk of material that must be gathered in the collapsing process. The excess material is usually tri-folded and sewn, making the finished product neater and somewhat easier to handle but not reducing the weight of the liner at all. Sometimes the excess material is cut away in an effort to reduce this weight and bulkiness, but this compromises the integrity of the sheet and each of the corners must be separately sealed.
To empty a modern tank of its remaining contents before collapsing the tank, one or more workers must manually grip handfuls of the wet floor panel on one side of the tank and lift the liner to force the remaining liquid toward a drain on the opposite side of the tank. They are often wearing gloves and working in cold conditions. The floor panel, as it is pulled, creates a vacuum with the ground and resists the process. This is a clumsy, difficult task and often results in damage to the liner.
To collapse a modern tank, the workers must perform a similar task as described with respect to emptying the tank, further complicated by the need to simultaneously cause the tank frame to collapse while gripping and pulling on the wet floor panel. This is even more clumsy and difficult and further imperils the liner.
It is, therefore, an object of this invention to provide a portable liquid storage tank which can be quickly opened, emptied and collapsed by one or two workers. Another object of this invention is to provide a portable liquid storage tank which is lightweight. A further object of this invention is to provide a portable liquid storage tank which is durable. Yet another object of this invention is to provide a portable liquid storage tank which is inexpensive. It is also an object of this invention to provide a portable liquid storage tank which has side walls and a floor panel not formed from one sheet of material. Still another object of this invention is to provide a portable liquid storage tank which does not have excess pleats of materials in its corners. An additional object of this invention is to provide a portable liquid storage tank which has less bulk of material to be gathered during the collapsing process. Another object of this invention is to provide a portable liquid storage tank which does not have corners compromised by cutting away excess material. A further object of this invention is to provide a portable liquid storage tank which does not require separate sealing of each of its corners. Yet another object of this invention is to provide a portable liquid storage tank which does not require gripping of handfuls of wet floor panel in order to empty or collapse the liner.